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About LinkBacksin case 0, (the initial state), there is a line that updates the variable 'state'. Same goes for case 1.Originally Posted by comocomocomo
This is a discussion on Switch-Case vs If-Else loops within the C Programming forums, part of the General Programming Boards category; Originally Posted by comocomocomo I don't know where is the bottleneck, but... But... wait a minute... The 'switch(state)' doesn't make ...
in case 0, (the initial state), there is a line that updates the variable 'state'. Same goes for case 1.
Yes, but this doesn't help, since 'state' is an automatic local variable, which gets initialized to 0 every time the processor enters the function. If the compiler follows the rules of the language, 'state' will always be 0 when the 'switch' is reached.
oh. so should i declare it as a global?
You don't need it in any other function, and global variables are bad. Leave it local but make it static. It will live like a global variable (whole program execution lifespan, initialized only once), but it will remain private to its function.
You are using MPLAB from memory -> But you still haven't told us what compiler you are using!
It would also depend on whether you are using the LITE/Standard/PRO (You pay more money, your code gets optimised more)
The best way would be to actually see what is being generated -> The switch statement is usually better when programming your PIC, because it generates an optimised branching table.
Do the two different ways in your code. Click "View" -> "Disassembly listing"
I'm using the C18 compiler PRO -
Code:280: if (test_data == 1) 039AE 0102 MOVLB 0x2 039B0 0E01 MOVLW 0x1 039B2 19FE XORWF 0xfe, W, BANKED 039B4 E101 BNZ 0x39b8 039B6 51FF MOVF 0xff, W, BANKED 039B8 E10C BNZ 0x39d2 281: { 282: puts("1"); 039BA 0E76 MOVLW 0x76 039BC 6EE6 MOVWF 0xfe6, ACCESS 039BE 0E4E MOVLW 0x4e 039C0 6EE6 MOVWF 0xfe6, ACCESS 039C2 0E00 MOVLW 0 039C4 6EE6 MOVWF 0xfe6, ACCESS 039C6 ECFA CALL 0x53f4, 0 039C8 F029 NOP 039CA 52E5 MOVF 0xfe5, F, ACCESS 039CC 52E5 MOVF 0xfe5, F, ACCESS 039CE 52E5 MOVF 0xfe5, F, ACCESS 283: } 284: else if (test_data == 2) 039D0 D04F BRA 0x3a70 039D2 0E02 MOVLW 0x2 039D4 19FE XORWF 0xfe, W, BANKED 039D6 E101 BNZ 0x39da 039D8 51FF MOVF 0xff, W, BANKED 039DA E10C BNZ 0x39f4 285: { 286: puts("2"); 039DC 0E74 MOVLW 0x74 039DE 6EE6 MOVWF 0xfe6, ACCESS 039E0 0E4E MOVLW 0x4e 039E2 6EE6 MOVWF 0xfe6, ACCESS 039E4 0E00 MOVLW 0 039E6 6EE6 MOVWF 0xfe6, ACCESS 039E8 ECFA CALL 0x53f4, 0 039EA F029 NOP 039EC 52E5 MOVF 0xfe5, F, ACCESS 039EE 52E5 MOVF 0xfe5, F, ACCESS 039F0 52E5 MOVF 0xfe5, F, ACCESS 287: } 288: else if (test_data == 3) 039F2 D03E BRA 0x3a70 039F4 0E03 MOVLW 0x3 039F6 19FE XORWF 0xfe, W, BANKED 039F8 E101 BNZ 0x39fc 039FA 51FF MOVF 0xff, W, BANKED 039FC E10C BNZ 0x3a16 289: { 290: puts("3"); 039FE 0E72 MOVLW 0x72 03A00 6EE6 MOVWF 0xfe6, ACCESS 03A02 0E4E MOVLW 0x4e 03A04 6EE6 MOVWF 0xfe6, ACCESS 03A06 0E00 MOVLW 0 03A08 6EE6 MOVWF 0xfe6, ACCESS 03A0A ECFA CALL 0x53f4, 0 03A0C F029 NOP 03A0E 52E5 MOVF 0xfe5, F, ACCESS 03A10 52E5 MOVF 0xfe5, F, ACCESS 03A12 52E5 MOVF 0xfe5, F, ACCESS 291: } 292: else if (test_data == 4) 03A14 D02D BRA 0x3a70 03A16 0E04 MOVLW 0x4 03A18 19FE XORWF 0xfe, W, BANKED 03A1A E101 BNZ 0x3a1e 03A1C 51FF MOVF 0xff, W, BANKED 03A1E E10C BNZ 0x3a38 293: { 294: puts("4"); 03A20 0E70 MOVLW 0x70 03A22 6EE6 MOVWF 0xfe6, ACCESS 03A24 0E4E MOVLW 0x4e 03A26 6EE6 MOVWF 0xfe6, ACCESS 03A28 0E00 MOVLW 0 03A2A 6EE6 MOVWF 0xfe6, ACCESS 03A2C ECFA CALL 0x53f4, 0 03A2E F029 NOP 03A30 52E5 MOVF 0xfe5, F, ACCESS 03A32 52E5 MOVF 0xfe5, F, ACCESS 03A34 52E5 MOVF 0xfe5, F, ACCESS 295: } 296: else if (test_data == 5) 03A36 D01C BRA 0x3a70 03A38 0E05 MOVLW 0x5 03A3A 19FE XORWF 0xfe, W, BANKED 03A3C E101 BNZ 0x3a40 03A3E 51FF MOVF 0xff, W, BANKED 03A40 E10C BNZ 0x3a5a 297: { 298: puts("5"); 03A42 0E6E MOVLW 0x6e 03A44 6EE6 MOVWF 0xfe6, ACCESS 03A46 0E4E MOVLW 0x4e 03A48 6EE6 MOVWF 0xfe6, ACCESS 03A4A 0E00 MOVLW 0 03A4C 6EE6 MOVWF 0xfe6, ACCESS 03A4E ECFA CALL 0x53f4, 0 03A50 F029 NOP 03A52 52E5 MOVF 0xfe5, F, ACCESS 03A54 52E5 MOVF 0xfe5, F, ACCESS 03A56 52E5 MOVF 0xfe5, F, ACCESS 299: } 300: else 03A58 D00B BRA 0x3a70 301: { 302: puts("?"); 03A5A 0E6C MOVLW 0x6c 03A5C 6EE6 MOVWF 0xfe6, ACCESS 03A5E 0E4E MOVLW 0x4e 03A60 6EE6 MOVWF 0xfe6, ACCESS 03A62 0E00 MOVLW 0 03A64 6EE6 MOVWF 0xfe6, ACCESS 03A66 ECFA CALL 0x53f4, 0 03A68 F029 NOP 03A6A 52E5 MOVF 0xfe5, F, ACCESS 03A6C 52E5 MOVF 0xfe5, F, ACCESS 03A6E 52E5 MOVF 0xfe5, F, ACCESS 303: } 304: 305: switch (test_data) 03A70 0E05 MOVLW 0x5 03A72 0102 MOVLB 0x2 03A74 19FE XORWF 0xfe, W, BANKED 03A76 E101 BNZ 0x3a7a 03A78 51FF MOVF 0xff, W, BANKED 03A7A E045 BZ 0x3b06 03A7C 0E04 MOVLW 0x4 03A7E 19FE XORWF 0xfe, W, BANKED 03A80 E101 BNZ 0x3a84 03A82 51FF MOVF 0xff, W, BANKED 03A84 E034 BZ 0x3aee 03A86 0E03 MOVLW 0x3 03A88 19FE XORWF 0xfe, W, BANKED 03A8A E101 BNZ 0x3a8e 03A8C 51FF MOVF 0xff, W, BANKED 03A8E E023 BZ 0x3ad6 03A90 0E02 MOVLW 0x2 03A92 19FE XORWF 0xfe, W, BANKED 03A94 E101 BNZ 0x3a98 03A96 51FF MOVF 0xff, W, BANKED 03A98 E012 BZ 0x3abe 03A9A 0E01 MOVLW 0x1 03A9C 19FE XORWF 0xfe, W, BANKED 03A9E E101 BNZ 0x3aa2 03AA0 51FF MOVF 0xff, W, BANKED 03AA2 E001 BZ 0x3aa6 03AA4 D03C BRA 0x3b1e 306: { 307: case 1: 308: puts("1"); 03AA6 0E76 MOVLW 0x76 03AA8 6EE6 MOVWF 0xfe6, ACCESS 03AAA 0E4E MOVLW 0x4e 03AAC 6EE6 MOVWF 0xfe6, ACCESS 03AAE 0E00 MOVLW 0 03AB0 6EE6 MOVWF 0xfe6, ACCESS 03AB2 ECFA CALL 0x53f4, 0 03AB4 F029 NOP 03AB6 52E5 MOVF 0xfe5, F, ACCESS 03AB8 52E5 MOVF 0xfe5, F, ACCESS 03ABA 52E5 MOVF 0xfe5, F, ACCESS 309: break; 03ABC D03B BRA 0x3b34 310: 311: case 2: 312: puts("2"); 03ABE 0E74 MOVLW 0x74 03AC0 6EE6 MOVWF 0xfe6, ACCESS 03AC2 0E4E MOVLW 0x4e 03AC4 6EE6 MOVWF 0xfe6, ACCESS 03AC6 0E00 MOVLW 0 03AC8 6EE6 MOVWF 0xfe6, ACCESS 03ACA ECFA CALL 0x53f4, 0 03ACC F029 NOP 03ACE 52E5 MOVF 0xfe5, F, ACCESS 03AD0 52E5 MOVF 0xfe5, F, ACCESS 03AD2 52E5 MOVF 0xfe5, F, ACCESS 313: break; 03AD4 D02F BRA 0x3b34 314: 315: case 3: 316: puts("3"); 03AD6 0E72 MOVLW 0x72 03AD8 6EE6 MOVWF 0xfe6, ACCESS 03ADA 0E4E MOVLW 0x4e 03ADC 6EE6 MOVWF 0xfe6, ACCESS 03ADE 0E00 MOVLW 0 03AE0 6EE6 MOVWF 0xfe6, ACCESS 03AE2 ECFA CALL 0x53f4, 0 03AE4 F029 NOP 03AE6 52E5 MOVF 0xfe5, F, ACCESS 03AE8 52E5 MOVF 0xfe5, F, ACCESS 03AEA 52E5 MOVF 0xfe5, F, ACCESS 317: break; 03AEC D023 BRA 0x3b34 318: 319: case 4: 320: puts("4"); 03AEE 0E70 MOVLW 0x70 03AF0 6EE6 MOVWF 0xfe6, ACCESS 03AF2 0E4E MOVLW 0x4e 03AF4 6EE6 MOVWF 0xfe6, ACCESS 03AF6 0E00 MOVLW 0 03AF8 6EE6 MOVWF 0xfe6, ACCESS 03AFA ECFA CALL 0x53f4, 0 03AFC F029 NOP 03AFE 52E5 MOVF 0xfe5, F, ACCESS 03B00 52E5 MOVF 0xfe5, F, ACCESS 03B02 52E5 MOVF 0xfe5, F, ACCESS 321: break; 03B04 D017 BRA 0x3b34 322: 323: case 5: 324: puts("5"); 03B06 0E6E MOVLW 0x6e 03B08 6EE6 MOVWF 0xfe6, ACCESS 03B0A 0E4E MOVLW 0x4e 03B0C 6EE6 MOVWF 0xfe6, ACCESS 03B0E 0E00 MOVLW 0 03B10 6EE6 MOVWF 0xfe6, ACCESS 03B12 ECFA CALL 0x53f4, 0 03B14 F029 NOP 03B16 52E5 MOVF 0xfe5, F, ACCESS 03B18 52E5 MOVF 0xfe5, F, ACCESS 03B1A 52E5 MOVF 0xfe5, F, ACCESS 325: break; 03B1C D00B BRA 0x3b34 326: 327: default: 328: puts("?"); 03B1E 0E6C MOVLW 0x6c 03B20 6EE6 MOVWF 0xfe6, ACCESS 03B22 0E4E MOVLW 0x4e 03B24 6EE6 MOVWF 0xfe6, ACCESS 03B26 0E00 MOVLW 0 03B28 6EE6 MOVWF 0xfe6, ACCESS 03B2A ECFA CALL 0x53f4, 0 03B2C F029 NOP 03B2E 52E5 MOVF 0xfe5, F, ACCESS 03B30 52E5 MOVF 0xfe5, F, ACCESS 03B32 52E5 MOVF 0xfe5, F, ACCESS 329: }
Fact - Beethoven wrote his first symphony in C
